Not all screws are the same. While all screws have a pointed end and a threaded shaft, they are available in different sizes. In addition to different lengths, you can find screws in different thread diameters. There are minor and major thread diameters, however. Both of these specifications refer to the size of a screw’s threading. With that said, minor and major thread diameters are two unique specifications
What Is Minor Thread Diameter?
Minor thread diameter is the smallest diameter of a screw’s threading that touches the roots. Roots, of course, are the deepest part of the groove. When inspecting a screw, you can find the roots between these threaded grooves. Minor thread diameter is a measurement of the smallest diameter that touches the roots.
What Is Major Thread Diameter?
Major thread diameter, on the other hand, is the largest diameter of a screw’s threading that touches the crests. All threaded fasteners have a minor thread diameter and a major diameter. For the major diameter, you’ll need to look for the crests. Crests are the outermost part of a screw’s threading. Major thread diameter is a measurement that corresponds with a screw’s crests.
Differences Between Minor and Major Thread Diameters
Screws don’t have uniform threading that’s the same size from top to bottom. All screws have helical threading, which allows them to dig into materials when driven via a handheld or powered screwdriver. As a result, minor and major thread diameters are used to express the size of their threading.
Minor thread diameter lives up to its namesake by representing the smallest diameter of the threading that touches the roots, whereas major thread diameter represents the largest diameter of the threading that touches the crests. When shopping for screws, you should consider both of these specifications. Checking a screw’s minor and major thread diameters will allow you to determine if it’s the right size for your fastening application. With that said, you’ll still need to consider the length.
Screws are available in different lengths. The length of a screw has no impact on the size of its threading. Threading is measured in diameter. There’s minor thread diameter, and there’s major thread diameter, neighter of which affect the length of a screw. By taking into account the thread diameters, as well as the length, you can choose screws in the right size for your fastening application.